<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <script>
        let arr = [23,4,75,2,6]

        let arr2 = arr.map(function (item,i){
            //副作用
            console.log(i)
            return item+1
        })

        let arr3 = arr.map((item,i) => item+2)

        console.log(arr)
        console.log(arr2)
        console.log(arr3)
    </script>
</body>
</html>